In advancement of digital technologies of electronic hardware in recent years, there has been an increasing demand for memory apparatuses having a larger capacity and nonvolatility, to preserve data of music, images, information, and so on. As one measure to meet the demand, a nonvolatile memory apparatus (hereinafter referred to as ReRAM) using a memory element including a resistance variable layer which changes its resistance value in response to electric pulses applied and maintains the changed state has attracted an attention. This is because the memory element can have a relatively simple structure, can be easily integrated to have a highly-dense structure, and is highly compatible with a conventional semiconductor process. In the ReRAM, it is required to develop a material capable of stably changing the resistance value with high reproducibility even when the memory element including the resistance variable layer is miniaturized, and a driving method thereof, and research and development for them has been vigorously made.
Patent document 1 discloses that a perovskite oxide is provided between a first electrode and a second electrode to form a resistance variable element, a voltage pulse with a fixed polarity is applied between the first electrode and the second electrode to cause electric resistance between the first electrode and the second electrode to change, and a change rate of the resistance value changes from positive to negative with an increase in a cumulated pulse application time associated with application of the voltage pulses. FIG. 12 is a view showing the relationship between the resistance value of the resistance variable material and a cumulated time of the voltage pulses applied which is disclosed in Patent document 1.
Non-patent document 1 discloses a method for permanently switching a resistance variable element using TiO2 from bipolar resistance switching to unipolar resistance switching.    Patent document 1: Japanese Laid-Open Patent Application Publication No. 2006-19444    Non-patent document 1: Schroeder H. and Jeong D. S., 2007, Resistive switching in a Pt/TiO2/Pt thin film stack-a candidate for a non-volatile ReRAM, Microelectronic Engineering, vol. 84, pp. 1982-1985